The present invention relates to a vehicular lamp of a type having a reflector mounted in a lamp body and a bulb attached to the reflector, in which the angle of the optical axis of the reflector body can be controlled by controlling the tilt angle of the reflector relative to the lamp body. More particularly, the invention relates to a socket cover for a vehicular headlamp which seals a rear opening of the lamp body in such a manner as to prevent water from entering the lamp chamber.
In a conventional headlamp, as shown in FIG. 6, a lamp cavity 52 is defined by a lamp body 50 and a front lens 51 attached to the edge of the front opening of the lamp body 50, and a reflector 53 is provided within the lamp cavity 52. The optical axis of the reflector 53 can be controlled relative to the lamp body 50 by means of an optical axis control device (not shown). A light bulb 56 is mounted on the lamp body 50 via a bulb socket 55 in an opening 54 formed in the rear of the reflector 53, with the filament of the light bulb 56 supported approximately at the focus point F of the reflector 53. It is possible to replace the bulb 56 by removing the bulb socket 55 from the rear of the reflector 53 via a rear opening edge 57 formed in the rear of the lamp body 50.
The bulb socket 55 is hermetically attached to the rear opening edge 57 of the lamp body 50 and the reflector 53 by means of a substantially cylindrical socket cover 58 molded from soft synthetic resin or rubber so as to prevent water from entering the lamp body 50. The socket cover includes a cylindrical portion 59 formed at the center thereof and fitted to the outer periphery of the socket 55 projecting to the rear in relation to the reflector 53, and a skirt portion 61 integrally connected with the cylindrical portion via a thin portion 60 and fitted to the outer periphery of the rear opening edge 57 of the lighting fixture 50. The thin portion 60 absorbs differences in pressure between the outside and inside of the lamp cavity 52 due to temperature changes induced by the turning on and off of the bulb 56, thereby preventing failures caused by pressure changes.
In the conventional socket cover 58 having the structure described above, a stopper projection edge 62 formed along the outer periphery of the rear opening edge 57 of the lamp body 50 is engaged with a stopper groove 63 formed along the inner circumferential surface of the skirt 61 of the socket cover 58, so that the stopper projection edge and the stopper groove are brought into close contact with each other. However, if a large difference in temperature occurs between the inside and the outside of the lamp cavity 52, water, such as rainwater, can be drawn into the lamp cavity 52 through the juncture the stopper projection edge and the stopper groove.
Moreover, the cylindrical portion 59 of the socket cover 58 is merely fitted to the outer periphery of the bulb socket 56 and not permanently sealed thereto. Therefore, the cylindrical portion 59 must be forcefully fitted around the socket 55 by reducing the bore of the cylindrical portion 59 in order to improve the contact between the cylindrical portion and the socket, thereby resulting in a difficult mounting operation.